1. Field of the Invention
The present invention relates to a high frequency, voltage mode control power converter, and more particularly to a power converter having a microprocessor applied to control the dead-time value of a pulse width modulation (PWM) controller so as to improve the output steady response of the power converter, and hence the efficiency of the power converter is raised.
2. Description of Related Art
A voltage feedback control loop is widely used in controlling a power converter. The basic conception of the voltage feedback control loop is that a voltage mode PWM controller (an integrated circuit) is used to control a power converter. When an oscillator in the voltage mode PWM controller continually generates a series triangle wave, the PWM controller synchronously turn on an active switch connected to a primary side of the power converter. As soon as an error amplifier in the voltage mode PWM controller receives a feedback output voltage from the power converter which generates an error signal intersecting the triangle wave, the active switch is turned off. By repeatedly turn on and turn off, the power in the primary side of the power converter is transferred to a secondary side of the power converter.
However, the power converter is only controlled by the voltage feedback control loop but without any current feedback, and hence the response of the power converter is totally depended on the output voltage of the power converter. In order to avoid the transient response of the output voltage becomes too slow, and for the purpose of decreasing the output ripple voltage, the bandwidth of the voltage feedback control loop is greatly raised. Once the bandwidth is over raised, some problems are occurred. A distortion phenomenon of an input current of the power converter is usually occurred, thus the root mean square value of the input current is also raised. A ripple of the input voltage is occurred as well and hence the input power is increased, so that the efficiency of the power converter is decreased.
On the contrary, if the bandwidth is lowered, the distortion phenomenon of the input current could be avoided, however the transient response of the output voltage becomes lower and the output ripple voltage is increased. Once the large transient response of the output voltage is occurred, the output voltage may become too high or low. If the output voltage is too high, some electrical components in the power converter are burned out because of the electrical stress problems.
If the current feedback control loop is applied to control the power converter, more electrical components, such as a current transformer, are needed, and hence the total cost of the power converter and circuit complexity are raised.
To overcome these shortcomings, the present invention tends to provide a high frequency, voltage feedback control mode power converter to mitigate and obviate the aforementioned problems.
The main objective of the invention tends to provide a power converter having a microprocessor applied to control the dead-time value of a pulse width modulation (PWM) controller so as to improve the total steady response, and raise the efficiency of the power converter.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.